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.\" $DragonFly: src/lib/libc/sys/mountctl.2,v 1.3 2008/02/10 23:35:30 swildner Exp $
.\"
.Dd July 21, 2009
.Os
.Dt MOUNTCTL 2
.Sh NAME
.Nm mountctl
.Nd execute a mount control operation
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/mountctl.h
.Ft int
.Fo mountctl
.Fa "const char *path"
.Fa "int op"
.Fa "int fd"
.Fa "void *ctl"
.Fa "int ctllen"
.Fa "void *buf"
.Fa "int buflen"
.Fc
.Sh DESCRIPTION
The
.Fn mountctl
system call executes the mount control operation
.Fa op
on the mount point
.Fa path .
An optional file descriptor
.Fa fd
can be passed, or set to -1 if unneeded.
The
.Fa ctl
argument is for passing operation specific data and usually points to
some struct (see
.Sx CONTROL OPERATIONS
for further information).
The data's size is specified by
.Fa ctllen .
The
.Fa buf
and
.Fa buflen
arguments are used if the operation needs to return data to the caller
or set to
.Dv NULL
and 0 if unused.
.Sh CONTROL OPERATIONS
The following operations are defined in
.In sys/mountctl.h :
.Bl -tag -width indent
.It Dv MOUNTCTL_SET_EXPORT
Set export control of a filesystem.
This operation needs a
.Vt struct export_args
passed in
.Fa ctl .
Note that export control for numerous filesystems may still only be settable
with
.Xr mount 2 .
New software should attempt to use
.Fn mountctl
before using the old
.Xr mount 2
method.
.It Dv MOUNTCTL_INSTALL_VFS_JOURNAL
Install a journal on a mount point.
This operation needs a
.Vt struct mountctl_install_journal
passed in
.Fa ctl .
The journal file must be specified via
.Fa fd .
A mount point may have multiple journals attached to it.
.It Dv MOUNTCTL_REMOVE_VFS_JOURNAL
Disassociate a journal from a mount point.
This operation needs a
.Vt struct mountctl_remove_journal
passed in
.Fa ctl .
.It Dv MOUNTCTL_RESTART_VFS_JOURNAL
Restart a journal with a new descriptor.
This operation needs a
.Vt struct mountctl_restart_journal
passed in
.Fa ctl .
The journal file must be specified via
.Fa fd .
.It Dv MOUNTCTL_STATUS_VFS_JOURNAL
Return a journal's status.
This operation needs a
.Vt struct mountctl_status_journal
passed in
.Fa ctl
and an array of
.Vt struct mountctl_journal_ret_status
in
.Fa buf .
.It MOUNTCTL_MOUNTFLAGS
It will store a comma separated string buffer in the
.Fa buf
parameter with the name list of the currently set
user mount flags. The
.Fa buf
will be sized at most
.Fa buflen
bytes.
.\" XXX Not yet implemented:
.\".It Dv MOUNTCTL_INSTALL_BLK_JOURNAL
.\".It Dv MOUNTCTL_REMOVE_BLK_JOURNAL
.\".It Dv MOUNTCTL_RESYNC_BLK_JOURNAL
.\".It Dv MOUNTCTL_RESYNC_VFS_JOURNAL
.\".It Dv MOUNTCTL_STATUS_BLK_JOURNAL
.El
.Sh RETURN VALUES
Upon successful completion, the number 
of copied bytes is returned; otherwise 
the value -1 is returned and the 
global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
The
.Fn mountctl
function will fail when one of the following occurs:
.Bl -tag -width Er
.It Bq Er EBADF
.Fa \&Fd
is not an active descriptor.
.It Bq Er EINVAL
The specified
.Fa ctllen
is not 0-1024,
.Fa buflen
is not 0-16384, or
.Fa path
is
.Dv NULL .
.It Bq Er EPERM
The caller is not the super-user.
.El
.Sh SEE ALSO
.Xr mount 2 ,
.Xr mountctl 8
.Sh HISTORY
The
.Fn mountctl
system call first appeared in
.Dx 1.1 .
.Sh AUTHORS
.An -nosplit
The
.Fn mountctl
system call was written by
.An Matthew Dillon
and this manual page was written by
.An Sascha Wildner .